Strange SMP6 wild things

I was in the smp6 wild and all of a sudden in red letters in the chat it said "The ground shakes nearby..." should I take caution, is it a bug, or a new thing in update, or awesome EMC scaring people. Let me know!

I lagged, turned around, and this thing called an "Enraged Skeleton" popped up. next thing I know, I'm at 2 hearts and it's in my face, I got some hits on it, though. Then I logged out, because it freaked me out, and I never read about the updates xDAnyone else fight one, and is there some "Weakness" to them, so I don't die the second I log back on?

I lagged, turned around, and this thing called an "Enraged Skeleton" popped up. next thing I know, I'm at 2 hearts and it's in my face, I got some hits on it, though. Then I logged out, because it freaked me out, and I never read about the updates xDAnyone else fight one, and is there some "Weakness" to them, so I don't die the second I log back on?

I lagged, turned around, and this thing called an "Enraged Skeleton" popped up. next thing I know, I'm at 2 hearts and it's in my face, I got some hits on it, though. Then I logged out, because it freaked me out, and I never read about the updates xDAnyone else fight one, and is there some "Weakness" to them, so I don't die the second I log back on?

Go Survival Update

I believe you are invincible for a couple of ticks so try to run away and box yourself in. Regen, then kill it.